Seismic Risk Maps Research Articles

Nationwide Earthquake Risk Model for Wood-Frame Houses in Canada

Quantitative seismic risk assessments involve hazard characterization, exposure database, vulnerability assessment, and uncertainty modelling, and promote consistent risk management actions, when conducted systematically across a country. This study implements a performance-based earthquake engineering methodology to develop a nationwide earthquake risk model for Canadian wood-frame houses by integrating probabilistic seismic hazard analysis results provided by the Geological Survey of Canada and seismic fragility functions derived from incremental dynamic analysis. To facilitate the implementation of the seismic risk analysis method, an in-house probabilistic seismic hazard analysis tool for Canada is developed and used to verify the accuracy of the adopted approach of approximating the upper tail of the seismic intensity measure distribution and to generate detailed seismic disaggregation results for ground motion record selection and seismic fragility modelling purposes. By integrating the preceding two elements via Monte Carlo methods, a full seismic risk curve can be obtained in a computationally efficient manner. The approach is applied to 1,620 representative locations used for the 2016 Canadian Census and thus facilitates the development of seismic risk maps of key risk metrics that are derived from exceedance probability curves in terms of earthquake damage/loss ratio. The developed seismic risk maps serve as valuable decision-support tools to implement risk-based management strategies consistently across Canada.

Integrated use of ambient vibrations and geological methods for seismic microzonation

ABSTRACT Ambient vibrations spectral ratios at forty-five sites and shear wave velocity profiles obtained by inverting surface waves dispersion curves were used to assess seismic site response properties in the Floridia village located in southeastern Sicily. The results of the horizontal-to-vertical spectral ratios analysis often indicate fundamental in the frequency range 1.5–4.0 Hz. Conversely, where the bedrock outcrop, spectral ratios are flat. The calcarenites outcropping in the north-west sector of the village and the soft sediments in the south-east are characterized by shear wave velocity of about 700 m/s and ranging between 200 and 600 m/s, respectively. The geological substratum has instead shear wave velocity of about 1500 m/s. The achieved geophysical and geological data help to build a subsoil model of the studied area, classifying the main lithotypes above the bedrock and determining the hidden morphology. Moreover, amplification functions were computed for zones with homogenous geological and geophysical properties. Therefore, these site amplification functions were used to simulate ground motion scenarios corroborating the efficiency of the obtained results. The used strategy, involving geophysical and geological methods, represents an important step to derive ground motion scenarios and seismic risk maps. Moreover, the characterization of amplification due to local site effects could help to understand the pattern and the damage distribution of historical earthquakes.

Seismic vulnerability assessment at urban scale using data mining and GIScience technology: application to Urumqi (China)

Seismic vulnerability assessments play a significant role in comprehensive risk mitigation efforts and seismic emergency planning, especially for urban areas with a high population density and a complex construction environment. Traditional approaches such as in situ fieldwork are accurate for conducting seismic vulnerability assessments of buildings; however, they are too much time and cost-consuming, especially in moderate to low seismic hazard regions. To address this issue, an integrated approach for a macroseismic vulnerability assessment composed of data mining methods and GIScience technology was presented and applied to Urumqi, China. First, vulnerability proxies were established via in situ data of buildings in the Tianshan District with an EMS-98 vulnerability classification scheme and two data mining methods, namely, support vector machine and association rule learning methods. Then, vulnerability proxies were applied to the Urumqi database, and the accuracy was validated. Finally, seismic risk maps were constructed through data consisting of direct damage to buildings and human casualties. The results indicated that the two data mining methods could achieve desirable accuracies and stabilities when estimating the seismic vulnerability. The seismic risk of Urumqi was estimated as Slight with a predicted number of 61,380 homeless people for a seismic intensity scenario of VIII.

EVALUATION OF SEISMIC HAZARD USING TECTONIC FAULT DATA: CASE OF BENI-CHOUGRANE MOUNTAINS (WESTERN ALGERIA)

Abstract: In the world, people are increasingly exposed to natural hazards such as earthquakes. To this end, seismic risk mapping remains an essential topic of study in order to minimize their destructive effects. These maps are needed for both seismic risk management and for the design of infrastructure. The challenge is to take into account local information provided by seismic sources (historical seismicity) as well as information related to active tectonic faults. In this article, we calculated the seismic risk in the Mascara Mountains (western Algeria) using the geo-metric characteristic of known faults. This study is based on an important collection of a tectonic database of these faults (Nature, geometry and geological context). This information is relevant for their seismic potential. Indeed, by including these formations we tried to compute the seismic risk this region characte-rized by weak seismicity. Our results show more or less alarming facts. Indeed, the magnitude values calculated are between 4.85 and 7.25, whereas the magnitudes obtained by experimental seismicity do not exceed 6 on the Richter scale. The values of the maximum ground acceleration (PGA) are between 0.03 and 0.28g. These results were compared with assessments made on the basis of historical seismicity; the maximum values obtained do not exceed 0.2 g. The higher values of magnitude calculated from the active faults is due to: (i) the nature of the faults (inverse, normal and strike slip), (ii) the geometry (length and depth) and (ii) that some of these faults may have an aseismic character.

A framework for assessing the seismic risk map of Italy and developing a sustainable risk reduction program

This work proposes a framework for the development of seismic risk maps at the nationwide scale. The seismic risk map is computed taking into account a seismogenic model of the analyzed area, and properly characterizing vulnerability and exposure of an asset of interest. A risk-targeted indicator named Municipal Expected Annual Loss (MEAL) is introduced and used as suitable metric for the development of the map, and for the subsequent seismic risk rating. The framework is then applied to show its usefulness in order to derive the seismic risk map of Italy considering the residential building stock as asset of interest. The proposed scientific approach for mapping seismic risk can be further used to develop a seismic risk reduction program and then evaluating its financial sustainability. The final part of the paper shows therefore a hypothetical seismic risk reduction program for the Italian residential building stock, estimating costs, benefits, and time-intervals required to guarantee its financial sustainability with the introduction of different taxation scenarios.

RISK-EU Method applied to the Algerian city of Arzew to assess exposure to earthquakes

In order To mitigate the adverse consequences of an earthquake, determining the vulnerability of buildings is imperative and crucial for saving human lives and buildings.So far, a good review / assessment of the RISK-EU method appears, as opposite to the other methods (more than a dozen) vulnerability assessment methods, to be by far the most suitable and applicable to the Context and seismographic configuration of Algeria,This tentative case study will review and evaluate, in particular, the RISK-EU method for Arzew city with due consideration to the following parameters:• Geographical position: North West of Algeria• Classified in Zone II, average seismicity area, in accordance with the Algerian seismic Rule - RPA99 version 2003-• The city suffered several earthquakes, the most recent one happened last Mars 21th, 2014 (Ms=4.3; equivalent to VI ≈ VII as per EMS 98),• The whole town is sitting on the rim between two tectonic plates and next to the Mediterranean Sea grand riftsThis study is based on the results of a survey assessing the exposure of the Arzew city buildings with a cross check and comparison with results obtained through the use of another method, widely used in Algeria, named « CTC ». This latter method is based on the assessment of the extent of the damages.For clarity sake and better understanding of our results, we have included in this study a « seismic risk map » Such map has been developed using a « SIG method » (Geographical information system)This study contains proposals to enhance the protection of the Arzew city buildings and reduce the overall risk and exposure to the frequent seismic activity in the Mediterranean area.

Finite-element 3D modeling of stress patterns around a dipping fault

Stresses in a block around a dipping fracture simulating a damage zone of a fault are reconstructed by finite-element modeling. A fracture corresponding to a fault of different lengths, with its plane dipping at different angles, is assumed to follow a lithological interface and to experience either compression or shear. The stress associated with the destruction shows an asymmetrical pattern with different distances from the highest stress sites to the fault plane in the hanging and foot walls. As the dip angle decreases, the high-stress zone becomes wider in the hanging wall but its width changes negligibly in the foot wall. The length of the simulated fault and the deformation type affect only the magnitude of maximum stress, which remains asymmetrical relative to the fault plane. The Lh/Lf ratio, where Lh and Lf are the widths of high-stress zones in the hanging and foot walls of the fault, respectively, is inversely proportional to the fault plane dip. The arithmetic mean of this ratio over different fault lengths in fractures subject to compression changes from 0.29 at a dip of 80° to 1.67 at 30°. In the case of shift displacement, ratios are increasing to 1.2 and 2.94, respectively.Usually they consider vertical fault planes and symmetry in a damage zone of faults. Following that assumption may cause errors in reconstructions of stress and fault patterns in areas of complex structural setting. According geological data, we know the structures are different and asymmetric in hanging and foot walls of fault. Thus, it is important to quantify zones of that asymmetry. The modeling results have to be taken into account in studies of natural faults, especially for practical applications in seismic risk mapping, engineering geology, hydrogeology, and tectonics.

Evaluation of Peak Ground Acceleration for the City of Kerman through Seismic Hazard Analysis

In this paper, Probabilistic Seismic Hazard Analysis (PSHA) approach is used to evaluate the distribution of Peak Ground Acceleration (PGA) and their corresponding probabilities for Kerman region in S-E of Iran. The geological and seismological data were integrated into a probabilistic seismic hazard model for the region. Historical and instrumental earthquake data, geology, tectonics, fault activity and seismic source models related to seismic events are taken into account. Foreshocks and aftershocks are rationally eliminated and main shock records are used to evaluate seismicity parameters using Kijko method. The use of such method is advantageous since it accounts for incomplete or inaccurate seismic data related to various seismic sources in the region. CRISIS2007 software is also used to carry seismic hazard analysis for the region and to develop the maps of iso-acceleration contours and for various return periods. The results have been displayed as the probabilistic estimates of PGA for the return periods of 50, 75 and 475 years. Comparison of the results obtained here with those suggested by Iranian Code of Practice for Seismic Resistance Design of Buildings (Standard No. 2800 Version 1393) are also presented. Results obtained in this study provides the basis for the preparation of seismic risk maps.

Recent developments for the seismic risk assessment

Thematic maps, such as seismic risk maps, are a useful tool that researchers use for representing the adverse outcomes that a natural catastrophic event can have over the territory. Generally, in those studies, major attention is focused in urban areas, where the human activities are concentrated. Main concerns are about the existing building stock, mostly composed by structures not compliant with modern seismic design criteria. The realization of a risk map is a complex task that involves the combination of data coming from different field of expertise, such as geology, geotechnical and structural engineering. The paper describes how the application of prospecting and surveying techniques (geological surveys, drilling, down-hole, MASW) allowed a decisive improvement in the geological knowledge of the area, contributing to define the subsoil model for the purposes of seismic microzonation. The interpretation of geophysical and geotechnical data and their correlation with geological units are explained and finally the microzonatic map is presented. The paper also reports the seismic geotechnical characterization executed with laboratory tests including the resonant column and cyclic torsional shear test on undisturbed samples. The results are summarized in terms of variation of stiffness and damping with shear strain. Finally, the use of wireless sensor technology for structural monitoring has significant benefits when the time available for access is often severely limited, by representing an effective way of managing risks once that an area of concern has been identified. The aim of the study is the acquisition of a local knowledge on issues related to seismic risk that may affect urban areas, through the acquisition, management and sharing of complex information. The available information, collected by sensor network, have been combined together in a Geographical Information System tool. The results provide a reliable representation of the seismic risk at urban scale to be used when planning the mitigation measures to be undertaken in order to improve the prevention and reduction of the disastrous effects of the earthquakes.

Seismic risk assessment and mapping at different levels

Earthquakes incur the greatest damage compared with all the other natural deleterious occurrences; when occurring in industrialized and densely populated regions, they can prove devastating. In the Russian Federation, we have more than 20 million people living in regions of moderate and high seismicity. The areas that are hit by earthquakes, with events of intensity VII (MMSK-86 scale) or greater occurring, make up approximately 20% of Russia’s area. The present paper addresses the methodological procedures of risk assessment and databases used for risk computations at different levels. The examples of seismic risk assessment and mapping at different levels: country, region and urban, are given. Special attention is paid to information and web technologies used for verification data on built environment inventory and vulnerability.

Insights into the possible seismic damage of residential buildings in Bucharest, Romania, at neighborhood resolution

Seismic loss estimation analysis for large cities is a very demanding yet necessary task; the modelling of such complex systems requires first of all insightful input data at good resolution, referring to local effects, buildings and socio-economic aspects. Also, the implementation of less empirical estimation methods is needed. Until recently, these requirements could not be fulfilled for Bucharest, the capital city in the European Union which is most at risk due to earthquakes. Based on 2011 and 2002 census data, standardized according to the framework of the Near-real time System for Estimating the Seismic Damage in Romania (SeisDaRo) through a unique approach, and on relevant hazard scenarios, we estimate for the first time the building damage at census tract scale. The methodology applied relies on 48 vulnerability curves for buildings, on the Improved Displacement Coefficient Analytical Method included in the SELENA software for computing damage probabilities and on deterministic seismic hazard scenarios, including the maximum possible earthquake. By using overlay analysis with satellite imagery and a new methodology integrated in GIS we show how results can be enhanced, reflecting more localized characteristics. Best practices for seismic risk mapping are also expressed. The results are promising and contribute to mitigation efforts in Bucharest.

The population in China’s earthquake-prone areas has increased by over 32 million along with rapid urbanization

Accurate assessments of the population exposed to seismic hazard are crucial in seismic risk mapping. Recent rapid urbanization in China has resulted in substantial changes in the size and structure of the population exposed to seismic hazard. Using the latest population census data and seismic maps, this work investigated spatiotemporal changes in the exposure of the population in the most seismically hazardous areas (MSHAs) in China from 1990 to 2010. In the context of rapid urbanization and massive rural-to-urban migration, nearly one-tenth of the Chinese population in 2010 lived in MSHAs. From 1990 to 2010, the MSHA population increased by 32.53 million at a significantly higher rate of change (33.6%) than the national average rate (17.7%). The elderly population in MSHAs increased by 81.4%, which is much higher than the group’s national growth rate of 58.9%. Greater attention should be paid to the demographic changes in earthquake-prone areas in China.

Earthquake Risk Assessment – Effect of a Seismic Event in a Moderate Seismic Area

This paper presents the process of earthquake risk analysis from the probabilistic determination of seismic hazard and local site effects, through the evaluation of building vulnerability to an event resulting in seismic risk maps. These results can then serve as useful tools for decision makers and insurance companies, and can be applied directly to overall risk management plans of cities. Finally a case study for seismic risk assessment performed in city of Győr is presented, taking into account local site effects based on response analysis with more than 6000 realizations and rapid visual screening of 5000 building to obtain the seismic risk.

Seismic vulnerability and risk assessment of Kolkata City, India

Abstract. The city of Kolkata is one of the most urbanized and densely populated regions in the world and a major industrial and commercial hub of the eastern and northeastern region of India. In order to classify the seismic risk zones of Kolkata we used seismic hazard exposures on the vulnerability components, namely land use/land cover, population density, building typology, age and height. We microzoned seismic hazard of the city by integrating seismological, geological and geotechnical themes in GIS, which in turn are integrated with the vulnerability components in a logic-tree framework for the estimation of both the socioeconomic and structural risk of the city. In both the risk maps, three broad zones have been demarcated as "severe", "high" and "moderate". There had also been a risk-free zone in the city that is termed as "low". The damage distribution in the city due to the 1934 Bihar–Nepal earthquake of Mw = 8.1 matches satisfactorily well with the demarcated risk regime. The design horizontal seismic coefficients for the city have been worked out for all the fundamental periods that indicate suitability for "A", "B" and "C" type of structures. The cumulative damage probabilities in terms of "none", "slight", "moderate", "extensive" and "complete" have also been assessed for the predominantly four model building types viz. RM2L, RM2M, URML and URMM for each seismic structural risk zone in the city. Both the seismic hazard and risk maps are expected to play vital roles in the earthquake-inflicted disaster mitigation and management of the city of Kolkata.

Probabilistic seismic hazard assessment for Central Asia

<p>Central Asia is one of the seismically most active regions in the world. Its complex seismicity due to the collision of the Eurasian and Indian plates has resulted in some of the world’s largest intra-plate events over history. The region is dominated by reverse faulting over strike slip and normal faulting events. The GSHAP project (1999), aiming at a hazard assessment on a global scale, indicated that the region of Central Asia is characterized by peak ground accelerations for 10% probability of exceedance in 50 years as high as 9 m/s<sup>2</sup>. In this study, carried out within the framework of the EMCA project (Earthquake Model Central Asia), the area source model and different kernel approaches are used for a probabilistic seismic hazard assessment (PSHA) for Central Asia. The seismic hazard is assessed considering shallow (depth < 50 km) seismicity only and employs an updated (with respect to previous projects) earthquake catalog for the region. The seismic hazard is calculated in terms of macroseismic intensity (MSK-64), intended to be used for the seismic risk maps of the region. The hazard maps, shown in terms of 10% probability of exceedance in 50 years, are derived by using the OpenQuake software [Pagani et al. 2014], which is an open source software tool developed by the GEM (Global Earthquake Model) foundation. The maximum hazard observed in the region reaches an intensity of around 8 in southern Tien Shan for 475 years mean return period. The maximum hazard estimated for some of the cities in the region, Bishkek, Dushanbe, Tashkent and Almaty, is between 7 and 8 (7-8), 8.0, 7.0 and 8.0 macroseismic Intensity, respectively, for 475 years mean return period, using different approaches. The results of different methods for assessing the level of seismic hazard are compared and their underlying methodologies are discussed.</p>

Seismic hazard and seismic risk assessment based on the unified scaling law for earthquakes: Himalayas and adjacent regions

For the Himalayas and neighboring regions, the maps of seismic hazard and seismic risk are constructed with the use of the estimates for the parameters of the unified scaling law for earthquakes (USLE), in which the Gutenberg-Richter law for magnitude distribution of seismic events within a given area is applied in the modified version with allowance for linear dimensions of the area, namely, logN(M, L) = A + B (5 − M) + C logL, where N(M, L) is the expected annual number of the earthquakes with magnitude M in the area with linear dimension L. The spatial variations in the parameters A, B, and C for the Himalayas and adjacent regions are studied on two time intervals from 1965 to 2011 and from 1980 to 2011. The difference in A, B, and C between these two time intervals indicates that seismic activity experiences significant variations on a scale of a few decades. With a global consideration of the seismic belts of the Earth overall, the estimates of coefficient A, which determines the logarithm of the annual average frequency of the earthquakes with a magnitude of 5.0 and higher in the zone with a linear dimension of 1 degree of the Earth’s meridian, differ by a factor of 30 and more and mainly fall in the interval from −1.1 to 0.5. The values of coefficient B, which describes the balance between the number of earthquakes with different magnitudes, gravitate to 0.9 and range from less than 0.6 to 1.1 and higher. The values of coefficient C, which estimates the fractal dimension of the local distribution of epicenters, vary from 0.5 to 1.4 and higher. In the Himalayas and neighboring regions, the USLE coefficients mainly fall in the intervals of −1.1 to 0.3 for A, 0.8 to 1.3 for B, and 1.0 to 1.4 for C. The calculations of the local value of the expected peak ground acceleration (PGA) from the maximal expected magnitude provided the necessary basis for mapping the seismic hazards in the studied region. When doing this, we used the local estimates of the magnitudes which, according to USLE, corresponded to the probability of exceedance 1% and 10% during 50 years or, if the reliable estimate is absent, the maximal magnitudes reported during the instrumental period. As a result, the seismic hazard maps for the Himalayas and the adjacent regions in terms of standard seismic zoning were constructed. Based on these calculations, in order to exemplify the method, we present a series of seismic risk maps taking into account the population density prone to seismic hazard and the dependence of the risk on the vulnerability as a function of population density.

A review of rotorcraft Unmanned Aerial Vehicle (UAV) developments and applications in civil engineering

Civil engineers always face the challenge of uncertainty in planning, building, and maintaining infrastructure. These works rely heavily on a variety of surveying and monitoring techniques. Unmanned aerial vehicles (UAVs) are an effective approach to obtain information from an additional view, and potentially bring significant benefits to civil engineering. This paper gives an overview of the state of UAV developments and their possible applications in civil engineering. The paper begins with an introduction to UAV hardware, software, and control methodologies. It also reviews the latest developments in technologies related to UAVs, such as control theories, navigation methods, and image processing. Finally, the paper concludes with a summary of the potential applications of UAV to seismic risk assessment, transportation, disaster response, construction management, surveying and mapping, and flood monitoring and assessment.

Seismic Risk at the Urban Scale: Assessment, Mapping and Planning

In the last decades the evaluation of the seismic risk is of rising concern, considered essential in the activity and definition of strategy planning and urban management. The evaluation of the seismic vulnerability of the existent building stock in the perspective of seismic risk mitigation should not be placed only in relation to the isolated buildings of relevant historical and cultural importance, but also, in relation to residential buildings within old urban centers. When assessing the seismic vulnerability of buildings it is essential to first establish the project objectives, before subsequently choosing the most appropriate strategy and tools necessary for building assessment and fulfillment of these objectives. It is also extremely important to understand the difference between the detailed approaches used for individual building assessment and those methods most efficient for larger scale analysis, pursued for city center assessment. In this work, the results attained from the vulnerability assessment of the old city center of Faro, in Portugal, allowed the estimation of physical damage scenarios, economical and human losses. The methodology applied herein and results are presented resourcing to a GIS application and database management system, enabling the storage of building features and survey, seismic vulnerability and risk mapping, as well as the continued upgrading and improvement of the collected data.

The Balei earthquake of 6 January 2006 (Mw = 4.5): a rare case of seismic activity in eastern Transbaikalia

The Balei earthquake of 6 January 2006 (Mw = 4.5) was felt over a large part of Transbaikalia. Judging by its updated source parameters (earthquake mechanism, seismic moment, and moment magnitude), the event was generated by the Balei–Darasun fault reactivated in the Cenozoic. Exhaustive macroseismic evidence has been collected for the first time from the study area. The reported results fill up the gap in the seismological knowledge of eastern Transbaikalia and can be used for seismic risk mapping and earthquake prediction.

Road density as a proxy for population density in regional-scale risk modeling

This paper examines the use of road network data as a proxy for interpreting population density, which is of use in regional-scale qualitative risk assessment for natural hazards. Comparison of available road network and population data at various scales in Ontario and Quebec yields a best-fit relationship of DP = 28 DR2. Analysis of available high-resolution topographic data for the Caribbean island nation of Saint Lucia suggests similar power law trends, with expected population density in Saint Lucia roughly half that of Canada for the same road density. Together, these findings suggest that DP ~ 10–30 DR2 may represent a useful range broadly applicable for a wide variety of geographic, climactic and socioeconomic settings. The Canadian relationship has been used to generate a population density model for the lowlands of eastern Ontario and southern Quebec, and this model has been compared with the spatial distribution of seismic hazard to develop a qualitative seismic risk map. The seismic risk map, presented primarily for illustrative purposes, shows elevated seismic risk in urban centers in the study area, and along a predominantly rural area east of Quebec City on both shores of the Saint Lawrence River.